Fluid heater support



March 1967 c. w. LAWTON 3,308,792

FLUID HEATER SUPPORT Filed Aug. 26, 1965 2 Sheets-Sheet 1 [/4 {Ill Ill I H6 1 CA/ZL WLAWTON INVENTOR.

March 1967 c. w. LAWTON FLUID HEATER SUPPORT 2 Sheets-Sheet 2 Filed Aug. 26, 1965 CARL W LAWTON INVENTOR BY 5 Kw.

United States Patent C) 3,308,792 FLUID HEATER SUPPORT Carl W. Lawton, West Hartford, Conn, assignor to Combustion Engineering, Inc., Windsor, Conn, a corporation of Delaware rags Aug. 26, 1965, Ser. No. 482,717 4 Claims. (Cl. 122510) This invention relates to fluid heaters and particularly to an apparatus for supporting the lower furnace wall tubes of a steam generator from the upper furnace wall tubes of the steam generator in a unit in which the furnace wall circuit contains a fluid mixing header.

All large steam generators are of the top supported design. Building steel supported on the ground is erected so that it passes over the steam generator with the upper portion of the steam generator being supported from this building steel. In these steam generators, which have vertical furnace wall tubes lining the walls of the furnace, the load of the lower portions of the furnace structure including burners, insulation, casing, etc. is carried by these vertical tubes.

In a once-through steam generator as the fluid is passed upwardly through the tubes of the furnace walls, the temperature of the fluid is increased due to radiation from the combustion occurring within the furnace. However, due to erratic slag patterns on the furnace walls and the distribution of the heat within the furnace, varying amounts of heat are picked up in different tubes. Therefore, the temperature of the fluid leaving the furnace wall tubes varies from tube to tube. This unbalance is magnified by the fact that the specific volume of the fluid increases as it becomes hot with this, in turn, tending to decrease the flow in that particular tube. With the decreased flow the tube gets even hotter resulting in more increase in specific volume. Although this phenomena generally does not occur to such as extent that the flow in the tube becomes completely unstable, it does operate to \magnify the temperature unbalance problem.

Obviously, one of the parameters which determine this unbalance is the amount of heat picked up in a single pass. In order to reduce the un'balances occurring in the furnace wall tubes, mixing headers have been introduced at a location within the furnace walls. The fluid then leaving the lower section of furnace wall tubes is mixed in this header so that it enters the upper section with a greatly decreased unbalance thereby decreasing the temperature unbalance at the outlet of the furnace wall.

In order to obtain this mixing the furnace wall tubes must be bent outwardly from the furnace wall and run to a mixing header. Since these furnace walls are structural members carrying vertical loads, a design must be developed to transfer the loading from the upper furnace wall tubes to the lower furnace wall tubes. This has been generally accomplished by intermeshin-g alternate tubes of the upper and lower section and bringing the tubes out at several different elevations. This dual location for the inlet and outlet of the furnace wall tubing results in considerable complication of the casing side of the furnace wall structure. In this area there are located on all large steam generators in addition to the insulation a multiplicity of buckstays running both in the horizontal and vertical direction. Since all of these tubes must be brought to a common mixing header, vertical runs are required outside the furnace and undesirable interference problems are encountered.

A large percentage of the heat absorbed in the furnace is absorbed in the lower portion of the furnace in the area of the burners. In order to obtain a good location for the mixing header with respect to the amount of heat picked up, it is desirable to locate this header at a relaice tively low elevation down almost as far as the burners, if possible. :In these areas, however, the heat absorption rate in the furnace walls is quite high. Therefore, structural members which form a portion of the furnace wall cannot be so designed that there is much distance between any portion of the fin and the fluid cooled tube to which it is welded. Excessive fin lengths result in high fin metal temperatures due to the heat flowing to the tube and, therefore, very low strengths.

In my invention a vertical bar is located intermediate adjacent tubes and extends upwardly passing between the tubes of the upper and lower sections. This bar replaces the tin which is welded intermediate these tubes and is securely welded to the adjacent tubes as well as to the fin above and below the bar. The tubes as they are bent outwardly from the furnace are seal welded to the bar and to each other. The vertical load is, therefore, transmitted from the upper tubes and webs to the vertical bar, through the vertical bar and to the webs and tubes of the lower section.

It is an object of my invention to provide a means for supporting the lower furnace walls and the upper furnace walls of a steam generator with the structural joint being such that the load transfer may be made in an area of high furnace heat absorption.

Other and further objects of my invention will become apparent to those skilled in the art as the description proceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired, as hereinafter more particularly set forth in the following detailed description of an illustrative embodiment, said embodiment being shown by the accompanying drawing wherein:

FIGURE 1 is a side elevation of a steam generator showing the general method of support;

FIGURE 2 is a side elevation showing a detail of the means of supporting the lower furnace wall tubes from the upper furnace wall tubes;

FIGURE 3 is a front elevation of the detail of FIG- URE 2; and

FIGURE 4 is a side elevation of an alternate method of supporting the lower furnace wall tubes from the upper furnace wall tubes which uses wide radius bends where the furnace wall tubes bend outwardly to the mixing wall header.

FIGURE 5 is a front elevation of the detail or FIG- UR'E 4.

In the illustration of FIGURE 1 fuel is introduced through burners 2 into the furnace 3 where combustion takes place with the combustion products passing outwardly from the furnace through flue 4. Feedwater to the stream generator passes from the economizer (not shown) to the furnace wall inlet headers 5. It passes upwardly through tubes '6 lining the walls of the furnace 3. These tubes are 1% inches outside diameter and have a web (8) inch thick and /2 inch wide intermediate adjacent tubes and welded to the adjacent tubes.

The tubes pass from the lower furnace wall section 9 and are bent outwardly to the mixing header 10. Tubes for the upper furnace walls 12, egress from the header 10 and pass upwardly along the furnace walls to the furnace wall outlet header 13. The steam passes from the wall outlet header 13 to the superheaters (not shown) and then to a steam turbine (not shown) for the generation of electric power.

The building steel verticals 17 support building steel horizontals .18 from which the steam generator is supported. Tie rods 19 support the upper furnace walls through lugs 20 from the horizontal building steel '18.

These lugs 23 are securely welded to the furnace wall tubes with the weight of the steam generator structure then being carried on these tubes.

FIGURES 2 and 3 show a detail of the furnace wall arrangement in the area of the mixing header 10. The lower furnace wall tubes 9 are 1% inch tubes on 1% inch spacing with webs 8 welded intermediate the tubes. These tubes are bent at 90 outwardly from the furnace to form horizontal section 22 after they pass into the lower portion of the mixing header 10. The mixing header 10 has a baffle plate 23 running throughout a portion of its length so that the water passing into the lower portion of the header must flow around this baffie plate so that flow from various tubes of the lower furnace is mixed before passing to the upper portion of the mixing header 10.

The upper furnace wall tubes 12 are also bent outwardly from the furnace at the same general location forming horizontal section 24 and being welded to receive fluid from the upper portion of the mixing header 10. The fluid after passing around the baflie 23 flows from the upper portion of the header into these tubes and upwardly through the furnace wall tubes 12 forming the upper portion of the furnace wall.

At a location about 12 inches above and below the junction of the upper and lower headers there are located field welds so that this mixing header assembly may be supported and simply installed in the unit during erection. A flat bar 25 is located so that it runs intermediate adjacent tubes throughout the 24 inches distance between field welds. This bar is located so that the support or furnace edge of the bar is about /s inch beyond the center line of the tube in such a manner that the front edge is flush with the welded web of tubes above and below this mixing header section. This will support the location of the supporting bar such that it replaces the web in this section which simplifies welding of the structure since the bar may be readily welded to the tubes from the furnace side. It also is a good location for the bar to pick up load from the welded webs without introducing excessive eccentricity in the loading. This bar is securely welded to the tubes on either side of the bar as well as to the web above the bar. The welding is continued to the bar as the tubes bend outwardly from the furnace throughout a portion of the 90 bend. In order to make the joint gas tight, the upper and lower tubes must be welded together, and this is best accomplished by the addition of a filler bar 27 which passes between the tubes and has a length such that it fits between the tube adjacent vertical bars. The weld between the bar and the tube is continued along this filler rod so as to completely seal the space between the tubes. This, of course, must be done not only with the upper tube 12 but also with the lower tube 9.

Since the center of gravity of the bar 25 is offset from the center of gravity of the tubes and webs, necessarily some eccentricity is introduced into the loading system. This bar must, therefore, be a sufficient width to resist the local bending imposed by this loading, the amount depending on the load being carried by the system; in this case for a load of kips per tube. In this embodiment where there are several 1% inch tubes with 0.20 inch wall thickness, the flat bar is /2 inch thick, to match the web width, and 3 inches deep.

The 90 bends where the upper and lower furnace wall tubes bend outwardly from the furnace are made on a 1 /2 inch radius. Bends of such short radius can only be made without excessive thinning of the walls by the hot bending process with each tube being bent individually. FIGURES 4 and 5 illustrate an alternate arrangement for the mixing header support in which the tubes are bent with a long radius bend. Such long radius permits not only cold bending but also permits the entire welded wall panel to be bent as a group rather than requiring the tubes to be bent individually. The general construction of this support is quite similar to that of FIGURE 2. However due to the long radius bends, an excessive amount of the bar is exposed to the radiant heat of the furnace. Because this bar has these portions considerably remote from the fluid cooled portion of the bar, they will become overheated and tend to burn away. In addition to burning away, however, cracks can easily originate in this high temperature area. These cracks once formed will be areas of stress concentration so that the crack propagates through the bar and tube resulting in either failure of the tube or the entire support assembly. The oxidation limit for the material is the maximum safe metal temperature. These limits are listed in Bulletin No. 26 of the National 'Iube Division of United States Steel.

Accordinly, the bar 25 is cut back in this area to avoid any section of the bar from having an excessive high temperature. This, of course, varies on the heat absorption rate in the general area of the bar as well as the material of the bar. In this embodiment where the bar ma terial is of 1% percent chrome steel, the bar should be cut back so that the calculated bar metal temperature will not exceed 1000 F. It is also recommended that this joint after welding be covered with high temperature refractory insulation as additional protection for these bars. -It is not recommended that the insulating material be considered in determining the temperature of the fin. This material often has a tendency to break out, and there is no assurance that it will exist throughout the life of the unit. In View of the seriousness of a failure in this area, it is unwise to depend on the fragile type insulation to protect the structural joint.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and the variations and modifications may be made therein without departing from the spirit and scope of the invention. 1 therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

What I claim is:

1. In a top supported fluid heater having a furnace and vertical tubes lining the walls of said furnace, a web intermediate adjacent tubes and welded to the adjacent tubes, a mixing header system receiving fluid from the tubes lining the lower portion of said furnace walls and discharging fluid to the tubes lining the upper portion of said furnace walls, an apparatus for supporting the lower portion of the furnace walls from the upper portion of the furnace walls comprising: the lower end of the tubes forming the upper portion of the furnace walls bent outwardly from the furnace at least the upper portion of the tubes lining the lower portion of the walls bent outwardly from the furnace at least 90", with the tubes of the upper and lower portions of the furnace being in line with each other; a flat bar located intermediate adjacent tubes throughout the area of the 90 ends and extending upwardly and downwardly through a portion of the straights of the furnace wall tubes; said flat bar having a depth in a direction perpendicular to the furnace Wall substantially greater than its width parallel to the furnace wall, and the furnace side edge of said bar being generally flush with the welded web connecting adjacent tubes at either end of the flat bar and forming a portion of the furnace side of the wall, said flat bar being welded to the welded web at each end of the flat bar; said flat bar being welded to the adjacent tubes throughout its entire length and the in line tubes of the upper and lower furnace portions being welded together at the 90 bend to form a gas-tight seal.

2. In a top supported fluid heater having a furnace and vertical tubes lining the walls of said furnace, a web intermediate adjacent tubes and welded to adjacent tubes, and a mixing header system receiving fluid from the tubes lining the lower port-ion of said furnace walls and discharging fluid to the tubes lining the upper portion of said furnace walls, an apparatus for supporting the lower portion of the furnace walls from the upper portion of the furnace walls comprising: the lower end of the tubes forming the upper portion of the furnace walls bent outwardly from the furnace at least 90; the upper portion of the tubes lining the lower portion of the walls bent outwardly from the furnace at least 90, with the tubes of the upper and lower portions of the furnace being in line with each other; a flat bar located intermediate adjacent tubes throughout the area of the 90 bends and extending upwardly and downwardly through a portion of the straights of the furnace wall tubes; the furnace side edge of said bar being generally flush with the welded web connecting adjacent tubes at either end of the fiat bar and being welded thereto; said fiat bar being welded to the adjacent tubes throughout its entire length and the in line tubes of the upper and lower furnace portions being welded together at the 90 bend to form a gastight seal; said fiat bar having a portion extending on the furnace side of the tubes in the area of the 90 bends; and said portion of the flat bar being cut back in the area of the 90 bends away from the furnace side to a sufii- References Cited by the Examiner UNITED STATES PATENTS 3,027,882 4/1962 Kolling 122510 3,162,179 12/ 1964 Strohrneyer 1226 3,202,135 8/ 1965 Schroedter 122406 References Cited by the Applicant FOREIGN PATENTS 3/ 1961 Great Britain. 6/1961 Great Britain.

KENNETH W. SPRAG'UE, Primary Examiner. 

1. IN A TOP SUPPORTED FLUID HEATER HAVING A FURNACE AND VERTICAL TUBES LINING THE WALLS OF SAID FURNACE, A WEB INTERMEDIATE ADJACENT TUBES AND WELDED TO THE ADJACENT TUBES, A MIXING HEADER SYSTEM RECEIVING FLUID FROM THE TUBES LINING THE LOWER PORTION OF SAID FURNACE WALLS AND DISCHARGING FLUID TO THE TUBES LINING THE UPPER PORTION OF SAID FURNACE WALLS, AN APPARATUS FOR SUPPORTING THE LOWER PORTION OF THE FURNACE WALLS FROM THE UPPER PORTION OF THE FURNACE WALLS COMPRISING: THE LOWER END OF THE TUBES FORMING THE UPPER PORTION OF THE FURNACE WALLS BENT OUTWARDLY FROM THE FURNACE AT LEAST 90*; THE UPPER PORTION OF THE TUBES LINING THE LOWER PORTION OF THE WALLS BENT OUTWARDLY FROM THE FURNACE AT LEAST 90*, WITH THE TUBES OF THE UPPER AND LOWER PORTIONS OF THE FURNACE BEING IN LINE WITH EACH OTHER; A FLAT BAR LOCATED INTERMEDIATE ADJACENT TUBES THROUGHOUT THE AREA OF THE 90* BENDS AND EXTENDING UPWARDLY AND DOWNWARDLY THROUGH A PORTION OF THE STRAIGHTS OF THE FURNACE WALL TUBES; SAID FLAT BAR HAVING A DEPTH IN A DIRECTION PERPENDICULAR TO THE FURNACE WALL SUBSTANTIALLY GREATER THAN ITS WIDTH PARALLEL TO THE FURNACE WALL, AND THE FURNACE SIDE EDGE OF AID BAR BEING GENERALLY FLUSH WITH THE WELDED WEB CONNECTING ADJACENT TUBES AT EITHER END OF THE FLAT BAR AND FORMING A PORTION OF THE FURNACE SIDE OF THE WALL, SAID FLAT BAR BEING WELDED TO THE WELDED WEB AT EACH END OF THE FLAT BAR; SAID FLAT BAR BEING WELDED TO THE ADJACENT TUBES THROUGHOUT ITS ENTIRE LENGTH AND THE IN LINE TUBES OF THE UPPER AND LOWER FURNACE PORTIONS BEING WELDED TOGETHER AT THE 90* BEND TO FORM A GAS-TIGHT SEAL. 